Tonight, NASA will launch the highly-anticipated Kepler spacecraft into orbit, the latest to search for new planets throughout the galaxy. And you can watch the liftoff live online.

Scientists hope that this satellite will be able to detect Earth-like planets by examining the transit of a planet passing in front of a star - essentially, a tiny dot passing in front of the our view of the star in question. By doing so, NASA says, researchers can "determine the percentage of terrestrial and larger planets that are in or near the habitable zone of a wide variety of stars."


With this knowledge, we will better understand not only the nature of solar systems in the surrounding regions of space, but also some basic properties of these solar systems. We may even discover a number of new, potentially habitable planets in the galaxy. While we certainly won't be able to colonize them ourselves (maybe someday), advances such as this can go a long way towards discovering other life forms out there.

During its time in space (around 3.5 years, according to the mission press kit, with the possibility that it will be extended an additional 3 years after that) Kepler is expected to monitor over 100,000 stars, and unlike most satellites, this instrument will not be placed in earth orbit - it will be in an Earth-trailing heliocentric orbit, which will provide a more stable platform for viewing the stars, with less interference from Earth's gravity.


Kepler is a small satellite in comparison to other star-gazing instruments like the Hubble Space Telescope. At nine feet in diameter, and fifteen feet long, it comes in at just around a ton in weight. Compare this to Hubble, which is the size of a bus. But its petite size makes Kepler easier to launch because no shuttle is required to take it to orbit - and it's relatively cheaper, coming in at 600 million dollars, as opposed to the 4 to 6 billion dollars that Hubble has accumulated over the years, including several vital repair missions.

The satellite is named for sixteenth century scientist Johannes Kepler, who was the first to explain planetary motion, a huge step towards our understanding of space.

Launch is expected for 10:49 EST tonight from Cape Canaveral Air Force Station in Florida. Watch it live on NASA TV

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Mission homepage. Photo courtesy of Ball Aerospace